To me, it seems that the turbo starts working as soon as the boost hits the base level of the actuator where as with Webbo's, it doesn't start working until it reaches the 1.2bar that his is set to, which obviously takes longer to achieve
Mark I think you might have it upside down mate
The turbo will start working immediately because the wastegate will be closed until the Greddy tells it to open, therefore I dont think "Start Boost / Set Gain" will affect spoolup.
Here's my (limited) understanding- the Start Boost / Set Gain is designed to overrule the actuator setting so if you have a 0.6bar actuator, you could put the Start Boost to 1.2 and it should keep the wastegate closed until that pressure, thereby allowing you to hold more boost later on. Maybe that's why yours, set at 0.65 or something, is tailing off later in the rev range?